Ok so.. you're saying that since it's been heated already, it will have already been tempered and softened? That might make sense - when he said he needed to apply heat, maybe tempering it is what he meant rather than actually hot working it.

To me, 'softer' suggests it's more ductile than in it's ex-factory form, so I should be ok to dimple it myself a bit. I don't think I can go anywhere near Salsa's original stays, but I could maybe add a few more mm which would bring the bike more in line with what you'd expect. There was tons of clearance on the original bike which was nice but perhaps not worth compromising strength for.

Re the shop - they've been around since 1973 and are a very famous name - one of few painting and repair shops that seem to be known nationally and the closest such place to me. Expensive, but I thought I was getting top notch work...